There are no copyright problems with what you propose for many long-dead artists, but there are certain less-long-dead artists whose estates and assigns vigorously pursue people doing this sort of thing. One example of this latter case is the people who own rights to a certain famous cartoon mouse.
You should make it clear that the works you sell are reproductions. You'd think nobody would be stupid enough to sue you for selling what they thought was an original Van Gogh, but you might be surprised.
All paintings (and all books, photographs, sculptures, musical compositions, and other copyrightable works) that were first published before 1923 are in the public domain in the United States and may be freely reproduced.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.